The present invention relates to an immunoregulator comprising a derivative of estradiol, which is represented by the following formula (I): ##STR2##
The immunoregulator according to the present invention has a small influence to the non-specific immunoreactions and is active specifically to the immunoreaction against an isoantibody.
The immunosuppressor such as cyclophosphamide, azathiopurine, prednisolone, cyclosporin A, etc., which has hitherto been used as the immunoregulator for suppressing the foreign body rejection reaction, so-called the immunorejection which is a problem in an organ transplantation, even suppresses the nonspecific immunoreaction which has no relationship with the immunorejection. Accordingly, it has a strong side effect that the immunological competence of a patient is reduced and a severe infectious disease is caused, and there are various restrictions in its clinical use. Consequently, the development of a substance which specifically suppresses the immunoreaction against the isoantibody controlling the immunorejection which is a problem in an organ transplantation, has been desired.
As a result of the present inventors' earnest studies for obtaining an immunoregulator which does not unnecessarily suppress the immunoreaction, specifically suppresses the immunoreactions in the necessary range, is small in toxicity and has an excellent effect, it has been found by the present inventors that an immunoregulator containing the derivative of estradiol represented by the above formula (I) is effective in the above object, and on the basis of their finding, the present invention have been completed.